1. Field of the Invention
The present invention relates to a steering structure of an outboard motor.
2. Description of the Background Information
As a method for steering a vessel with an outboard motor, a system is known in which a steersman swings a steering handle provided at the front portion of the outboard motor to the right and left, thereby the outboard motor is steered to the right and left.
There is another example of such a steering structure, wherein a steering adjuster 1 as shown in FIG. 7 is mounted on an outboard motor 2 to prevent shocks to the outboard motor 2 from being transmitted to the steersman during steering. The steering adjuster 1 includes a rod-shaped adjuster arm 4, an end of which is rotatably attached to steering bracket 3 of the outboard motor 2 to which the steering handle is attached, a resistance nut 7, which is provided on clamp bracket 6 for mounting the outboard motor 2 to the vessel body via swivel bracket 5, and an adjuster shift 8 slidably inserted into the tightening portion 7a of the resistance nut 7, and the other end of the adjuster arm 4 is rotatably attached to the free end of the adjuster shaft 8.
A winged screw 9 on the tightening portion 7a is tightened to impart resistance to the sliding of the adjuster shaft 8 in order to absorb shocks exerted to the outboard motor 2.
The steering adjuster having the above structure becomes unable to fulfill inherent functions if the resistance nut exhibits less resistance when oil is adhered to the tightening portion at which resistance is generated, and when vibrations from the engine loosen the winged screw.
The present invention is made in view of the above, and an object of the present invention is to provide a steering structure of an outboard motor, which has no deterioration in functions and is highly reliable.
In order to solve the above problems, according to a first aspect of the invention, a steering structure of an outboard motor mounted on a vessel body via a bracket device and rendered steerable in a transverse direction of the vessel body by a steering handle is provided. The steering structure includes a tilting shaft positioned on the bracket device for pivotally supporting the outboard motor in such a manner that the outboard motor is vertically tilted. A steering damper is disposed in front of the outboard motor, below a steering bracket having a steering handle-mounting portion, and in front of the bracket device. The steering damper includes a damper cylinder positioned parallel to the tilting shaft and a piston rod that extends through the inside of the damper cylinder, extends parallel to the tilting shaft, and protrudes outwardly from the damper cylinder. Openings at opposite ends of the damper cylinder are closed by a piston stopper, which slidably supports the piston rod and maintains the inside of the damper cylinder fluidtight, to for a fluid chamber inside the damper cylinder. A damper piston for partitioning the oil chamber into right and left chambers is provided intermediate the ends of the piston rod positioned inside the fluid chamber. The right and left fluid chambers are intercommunicated by a bypass pipe, and a throttle valve is provided on the bypass pipe.
According to a second aspect of the invention, the damper cylinder and the steering bracket are linked to each other by a steering arm.
According to a third aspect of the invention, the throttle valve is disposed in front of the damper cylinder. The throttle valve is provided with an adjusting knob for varying a flow resistance value, the adjusting knob being disposed in a condition where the front surface thereof is perpendicular to a shaft portion thereof.
According to a fourth aspect of the invention, the throttle valve is disposed on the centerline of the forward direction of the outboard motor.
According to a fifth aspect of the invention, the throttle valve is disposed above the damper cylinder.
According to a sixth aspect of the invention, each end of the piston rod is fixed to one end of each of a pair of horizontally disposed right and left piston rod holders, the other ends of the pair of piston rod holders are disposed at opposite sides of the bracket device, and the piston rod holders and the bracket device are connected together on the tilting shaft.
As described above, the present invention provides a steering structure of an outboard motor mounted on a vessel body via a bracket device and made steerable to the right and left by means of a steering handle. The steering structure includes a tilting shaft provided on the bracket device to pivotally support the outboard motor in such a manner that the outboard motor can vertically tilt. A steering damper is disposed in front of the outboard motor, below a steering bracket having a steering handle-mounting portion, and in front of the bracket device. The steering damper includes a damper cylinder disposed parallel to the tilting shaft and a piston rod that extends inside the damper cylinder, extends parallel to the tilting shaft, and protrudes outwardly from the damper cylinder in the transverse direction. Openings at opposite ends of the damper cylinder are closed by a piston stopper, which slidably supports the piston rod and maintains the inside of the damper cylinder fluidtight, to form a fluid chamber inside the damper cylinder. A damper piston for partitioning the fluid chamber into right and left chambers is provided intermediate the ends of the piston rod positioned inside the fluid chamber. The right and left fluid chambers are intercommunicated by a bypass pipe, and a throttle valve is provided on the bypass pipe. According to this construction, the steering damper isolates a steersman from shocks that are unexpectedly exerted on the outboard motor during steering of the outboard motor. In addition, the damper performance is improved so as to be highly reliable.
The damper cylinder and the steering bracket are linked with each other through the steering arm. This construction simplifies the structure of the outboard motor.
Furthermore, the throttle valve is disposed on the centerline of the forward direction of the outboard motor in front of and above the damper cylinder. The throttle valve is provided with an adjusting knob for varying a flow resistance value. The adjusting knob is disposed so that the front surface is vertical. Such a construction allows the damper performance to be set according to a preference of the steersman, improves steerability, and makes adjustments of the throttle valve easy.
Moreover, each end of the piston rod is fixed to one end of a pair of horizontally extending piston rod holders, while the other ends of the piston rod holders are disposed on opposite sides of the bracket device. The piston rod holders and the bracket device are connected together on the tilting shaft. This construction makes the entire device compact and simplifies the structure.
In another aspect of the present invention, a damping structure is provided for a steering structure of an outboard motor, the steering structure including a steering handle mounting portion, and the outboard motor including a mounting bracket for mounting the outboard motor on a vessel. The damping structure includes a double acting fluid damper operatively connected between the steering handle mounting portion and the mounting bracket, whereby the damper permits normal steering of the vessel by pivoting of the motor but alleviates and absorbs shocks that are exerted on the motor so that such shocks will not be transmitted to a steersman.
In a further aspect of the present invention, the double acting fluid damper includes a damper cylinder having openings at opposite ends thereof, and a piston rod that extends through the inside of the damper cylinder and protrudes outwardly from the damper cylinder at opposite ends thereof. The openings of the damper cylinder are each closed by a piston stopper, which slidably supports the piston rod and maintains the inside of the damper cylinder fluidtight thereby forming a fluid chamber inside the damper cylinder, and a damper piston that partitions the fluid chamber into right and left fluid chambers is provided intermediate the ends of the piston rod positioned inside the fluid chamber. A fluid provided within the fluid chamber, and a bypass pipe interconnects the right and left fluid chambers to permit fluid to pass between the right and left fluid chambers.
In another aspect of the present invention, a throttle valve may be provided on the bypass pipe to regulate the flow of fluid between the chambers. Additionally, the throttle valve may be disposed in front of the damper cylinder, and the throttle valve may be provided with an adjusting knob for varying a flow resistance value, the adjusting knob being disposed in a condition where a front surface thereof extends generally vertically. Also, the throttle valve may be disposed above the damper cylinder.
In a further aspect of the present invention, each end of the piston rod is fixed to one end of a pair of horizontally disposed right and left piston rod holders, and the other ends of the pair of piston rod holders are disposed at opposite sides of the mounting bracket.
In other aspects of the present invention, the damper fluid may include one of a liquid and a gas. Furthermore, the liquid may be oil, and the gas may be nitrogen.
According to another aspect of the present invention, a steering structure of an outboard motor mountable on a vessel body via a bracket device and rendered steerable in a transverse direction of the vessel body by a steering handle. The steering structure includes a tilting shaft positioned on the bracket device for pivotally supporting the outboard motor in a manner such that the outboard motor is vertically tiltable, and a steering damper disposed in front of the outboard motor, below a steering bracket having a steering handle-mounting portion, and in front of the bracket device. The steering damper includes a damper cylinder having openings at opposite ends thereof, a piston rod extending through the inside of the damper cylinder and protruding outwardly from the damper cylinder at opposite ends thereof. The openings of the damper cylinder are each closed by a piston stopper, which slidably supports the piston rod and maintains the inside of the damper cylinder fluidtight to form a fluid chamber inside the damper cylinder, and a damper piston that partitions the fluid chamber into right and left fluid chambers is provided intermediate the ends of the piston rod positioned inside the fluid chamber. A fluid provided within the fluid chamber, and a bypass pipe interconnects the right and left fluid chambers to permit fluid to pass between the right and left fluid chambers.
A throttle valve may be provided on the bypass pipe to regulate the flow of fluid between the chambers, and the throttle valve may be disposed in front of the damper cylinder. The throttle valve may also be provided with an adjusting knob for varying a flow resistance value, the adjusting knob being disposed in a condition where a front surface thereof is generally vertical. The throttle valve may be disposed on the centerline of a forward direction of the outboard motor, and the throttle valve may be disposed above the damper cylinder. Furthermore, the damper cylinder and the steering bracket may be linked together through a steering arm.
In another aspect of the present invention, each end of the piston rod may be fixed to one end of a pair of horizontally disposed right and left piston rod holders, the other ends of the pair of piston rod holders are disposed at opposite sides of the bracket device, and the piston rod holders and the bracket device are connected together on the tilting shaft.
In further aspects of the present invention, the fluid may include one of a liquid and a gas. The liquid may be oil, and the gas may be nitrogen.